1. Field of the Invention
This invention relates to a gas generating apparatus used for inflating an air bag such as one used for a safety apparatus for protection against collision, life bag, rubber boat, escape chute, etc. More particularly, this invention concerns a gas generating apparatus for inflating an air bag whereby any shortfall in the quantity of gas required for inflating the air bag can be overcome by replenishing the air bag with air.
2. Statement of the Prior Art
Conventionally, in a passenger car, a safety apparatus adapted to protect passengers against physical shock at the time of a collision comprises an air bag with a volume of 60 liters and a gas generating apparatus which inflates this air bag, the gas generating apparatus being filled either with an explosive or a gas generating agent comprising similar constituents which is ignited and burnt at the time of a collision so as to immediately inflate the air bag with the gas generated thereby, thus protecting the driver from the effects of the collision, and preventing him from being seriously injured.
In such an apparatus, the quantity of gas generating agent required for inflating the air bag is between 70 and 100 g, and the total weight of the body of the gas generator is between 600 and 1100 g. With the above apparatus, the air bag is inflated merely by the generation of gas upon combustion of the gas generating agent; therefore, even an air bag with a 60-liter volume uses from 70 to 100 g of the generated gas, which is a relatively large amount, for the gas inflation. Consequently, the volume of the combustion chamber in the body of the gas generator has to be increased so that the gas generator becomes inevitably large in size and weight. In addition, since a relatively large amount of gas generating agent is burnt, the temperatures of the gas and the body of the gas generator becomes high, which involves such hazards as the possibility of passengers being burnt.
If the gas generating apparatus is accordingly reduced in size and weight with a corresponding reduction in the quantity of gas generating agent used therein, the air bag is not inflated to a sufficient extent and its function as a safety apparatus in time of collision is thereby compromised owing to the reduction in the amount of gas generated. Therefore, the shortfall in the quantity of gas generated needs to be overcome by supplementing the gas with air or the like.
For this purpose, it is conceivable to incorporate in the gas generating apparatus either an air ejector for replenishing air by ejecting a high-pressure gas, or a vapor ejector. However, since the primary high pressure gas in these kinds of ejector has a pressure as low as 10 kg/cm.sup.2 or less, such an ejector also needs to be relatively increased in size to be effective when used with such an air bag in a safety apparatus of the type described in order that a sufficient amount of air can be sucked in some tens of milliseconds.
Accordingly, such a gas generating apparatus is inevitably increased in size and weight and this means that it remains impossible for this type of bag to be used as an air bag for an automobile.